Variable nip press having rolls maintained on parallel axes

ABSTRACT

A press comprising a plurality of press rolls rotatable about parallel axes, wherein one of the press rolls is laterally movable relative to the other to vary the cross-section of the therebetween nip. Pressing force is applied to the laterally movable press roll by a plurality of separate link systems actuated by individual fluid pressure operated actuators; and the link systems are interconnected by a torsion bar which causes the link systems to maintain the axes of the press rolls parallel.

United States Eatent 1191 Stirk et a1.

1 51 May1,i973

[ VARIABLE NIP PRESS HAVING ROLLS MAINTAINED ON PARALLEL AXES [75] lnventors: Sidney E. Stirk; John P. Rich, both of Nashua; Russell E. Holt, Candia, all of NH.

[73] Assignee: Improved Machinery Inc., Nashua,

122 F1160; 11111622, 1971 21 App1.No.: 155,441

52 us. c1. ..100/121, 100/170, 162/46 51 1111.0 .13301 9/20, 1330b 3/04 [58] Field of Search ..100/163, 164, 168, IUD/169,170, 171, 116, 121; 162/301, 303,

[56] References Cited UNITED STATES PATENTS 1,194,266 8/1916 Alvord IOU/121 2,312,726 3/1943 Munr0.... ,...1()O/46 X 2,374,046 4/1945 Stacom ..100/l70 X 2,404,946 7/1946 Clem ..l00/ 168 X 2,738,663 3/1956 Moore 100/1 70 X 2,823,535 2/1958 Warner 100/170 X 3,269,303 8/1966 Qviller ..l0O/121 3,460,467 8/1969 Nystrom... lOO/lZl 3,527,159 9/1970 Edwards 100/170 3,653,320 4/1972 Oehlmann et a1. 100/168 Primary ExaminerPeter Feldman Att0rneyFrank S. Troidl et a1.

[57 ABSTRACT A press comprising a plurality of press rolls rotatable about parallel axes, wherein one of the press rolls is laterally movable relative to the other to vary the cross-section of the therebetween nip. Pressing force is applied to the laterally movable press roll by a plurality of separate link systems actuated by individual fluid pressure operated actuators; and the link systems are interconnected by a torsion bar which causes the link systems to maintain the axes of the press rolls parallel.

20 Claims, 7 Drawing Figures Patented May 1, 1973' 3 Sheets-Sheet 1 SIDNEY 5. $7'//?/( JOHN P. R/CH RUSSELL E. HOLT 'ATTORNEY Patented May 1, 1973 3,730,079

3 Sheets-Sheet 2 INVENTORS S/D/VEY E. ST/RK JOHN R C H RU S SELL E. HOL r ATTORNEY Patented May 1, 1973 3 Sheets-Sheet 5 s m WM V. m5 5 n m qd,

JOHN P. RICH RUSSELL E. HOLT VARIABLE NIP FRESS HAVING ROLLS MAINTAINED ON PARALLEL AXES The present invention relates to presses of the type including a plurality of press rolls spaced by a therebetweenv space or nip in which the material is pressed.

Conventionally, presses of this general type are employed in many different applications including, for example, the pressing of liquid suspensions such as pulp and effluent sludge. In presses of this type intended for pressing liquid suspensions, at least one of the press rolls must be laterally movable relative to the other to vary the cross-section of the nip whereby relatively large foreign and tramp material can pass therethrough, otherwise damage to the expensive press rolls and/or other parts of the press may occur. Also, during the pressing operation, the axes of the press rolls must be maintained parallel to provide uniform dryness of the discharged pressed material, provide a pressed mat of uniform cross-section, permit effective sealing at the ends of the rolls, and insure satisfactory driven rotation of the laterally movable press roll. Conventional presses wherein the press rolls are relatively laterally movable are, however, normally unable to maintain the axes of the press rolls parallel.

The principal object of the present invention is to provide a new and improved press of the type set forth particularly constructed and arranged to maintain the axes of the press rolls parallel while permitting relative lateral movement of the press rolls.

Another object of the invention is to provide a new and improved press of the type set forth particularly constructed and arranged to reduce frictional effects occuring during its operation.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein a preferred embodiment of the invention has been shown for the purposes of illustration only.

In accordance'with the invention, a press may comprise a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between the press rolls, one of the press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of the nip, first means actuatable for applying pressing force to the movable press roll and permitting lateral movement of the movable press roll away from the other press roll, second means actuatable for applying pressing force to the movable press roll and permitting lateral movement of the movable press roll away from the other press roll, control means for causing the first and second force applying means to maintain the axis of the movable press roll parallel to the axis of the other press roll, the first and second force applying means being spaced apart longitudinally of the movable press roll, the control means comprising connecting bridge means extending longitudinally along the movable press roll and interconnecting the force applying means to cause movement of one thereof to provide corresponding movement of the other thereof, and actuating means for actuating the first and second force applying means to apply said pressing force.

Referring to the drawings:

FIG. 1 is an elevational side view of a press including one embodiment of the invention;

FIG. 2 is an elevational end view of the press illustrated in FIG. 1;

FIG. 3 is an enlarged, fragmentary, elevational side view, partially broken away and in section, of the press shown in FIGS. 1 and 2;

FIG. 4 is a fragmentary, elevational, sectional view through the press rolls of such press;

FIG. 5 is an enlarged, fragmentary, perspective view of the pressing force applying means of the press;

FIG. 6 is an enlarged, fragmentary, perspective view illustrating one of the pressure blocks of the force applying means; and

FIG. 7 is an enlarged, fragmentary, elevational sectional view taken on Line 7 -7 of FIG. 5, looking in the direction of the arrows.

Referring more particularly to the drawings wherein similar reference characters designate corresponding parts throughout the several views, FIGS. 1 through 7 illustrate a press embodying the invention particularly adapted for pressing a liquid suspension such as, for example, pulp or effluent sludge. The illustrated press comprises a tank or vat, designated generally as 10, at opposite ends supported by pedestals 12 on supporting piers or foundations I4 and having one or more cleanout doors l6 permitting access to the vat interior for maintenance purposes. The vat 10 is provided with an inlet duct I8, adapted for connection to a pressurized source (not shown) of the suspension to be pressed, which is connected to the lower end of the vat interior through a plurality of inlet pipes 20 and communicating inlet openings 22 in the vat floor. The vat 10 is provided with a discharge conduit 24 open throughout the length of the vat 10 to the upper end of the vat interior to receive pressed solid material therefrom, the

.discharge conduit 24 containing a conventional feed screw 26 constructed to shred the received pressed solid material and convey the shredded material through the conduit 24 towards its discharge 28. The

feed screw 26 is mounted on a rotatable shaft 30 also carrying a conventional gear-type speed reducer 32 having a pulley wheel 34 on its input shaft 36; and the screw 26 and shaft 30 are rotatably driven through the speed reducer 32 by a conventional rotary output drive motor (not shown) and a drive belt 38 drivingly interconnecting the motor with the pulley wheel 34.

A pair of press rolls 40, 42 are rotatably mounted on parallel axes in the vat 10 circumferentially spaced by a therebetween nip M which along its upper end communicates with the discharge conduit 24 and its lower end communicates with the inlet openings 22. The press rolls 40, 42, as shown in FIG. 4, are provided with individual doctor blades 46, 48 which remove pressed solid material from the outer circumferences of the rolls 40, 42 whereby the removed material is discharged to the conduit 24 and its contained feed screw 26. The rolls 40, 42 each contain pluralities of axial liquid or filtrate discharge channels 50 spaced around their hubs 56 by separating ribs 52; and the circumferential walls 54 of the rolls 40, 42 are porous to drain liquid or filtrate to the channels 50. The vat 10 is provided with filtrate drainage conduits 5% for discharging liquid from the channels 50 at each end of each of the press rolls 40, 42; and an arcuate seal (not shown) is positioned at each end of each roll 40, 42 for preventing leakage around the roll ends. Also, flexible sealing means (not shown) are provided parallel to the roll axes for sealing the vat longitudinally of the rolls 40, 42.

The hubs 56 of the press rolls 40, 42 include integral stub shafts 60 which project from their opposite ends and rotatably mount the ends of the rolls 40, 42 on pairs of carriage blocks 62, 64, respectively. The carriage blocks 64 are rigidly mounted in fixed position such that their carried roll 42 is rotatable about a stationary axis; the carriage blocks 62 are slidably movable toward-and-away from the carriage blocks- 64 to laterally move their carried roll 40 towards-and-away from the roll 42 and thereby vary the cross-section of the nip 44. Each carriage block 62 is affixed to one end of upper and lower tie rods 66 which slidably extend through bores in the carriage blocks 64 and have their other ends on the opposite side of the press roll 42 from the press roll 40. A platen 68 is affixed to the latter mentioned ends of the tie rods 66 connected to each of the carriage blocks 62 so that the platens 68 are resultantly conjointly laterally movable with the carriage blocks 62 and their supported roll 40.

Pneumatically expansible springs or tubes 70 are located adjacent opposite sides of the nip 44 intermediate the thereadjacent carriage blocks 62, 64 and exert biasing forces on the carriage blocks 62 urging the roll 40 away from the roll 42. The expansible tubes 70 are connected by individual air supply conduits 72 to a relatively large common source or tank 74 of pressurized air at constant pressure; and the expansible tubes 70 thus exert constant equal biasing forces on the carriage blocks 62 and their carried press roll 40.

The rolls 40, 42 are rotatably driven in the opposite rotary directions schematically depicted by the arrows in FIGS. 3 and 4 through a drive means comprising a rotatable main drive shaft 76 adapted to be coupled to a conventional rotary drive motor (not shown). The main drive shaft 76 is drivingly connected to one of the stub shafts 60 supporting the press roll 42 by conventional gearing contained within a gear housing designated generally as 78; and the stub shaft 60 at the opposite end of the roll 42 is drivingly connected to the thereadjacent stub shaft 60 supporting the roll 40 by conventional gearing contained within a gear housing 80. The teeth of the intermeshing gears in the gear housing 80 are, as will be understood, sufficiently deep to permit limited lateral movement of the press roll 40 and its stub shafts 60 relative to the press roll 42 and its stub shafts 60 without interrupting the driving connection between the stub shafts 60 for the rolls 40, 42.

Pressing force is applied to the press roll 40 by a pair of link systems or means 82, 84 laterally spaced apart longitudinally of the press roll 40 and acting on the latter through the platens 68, tie rods 66 and carriage blocks 62. The link systems 82, 84 are of identical construction and arrangement to be of equal mechanical advantage and include links so oriented and proportioned that they produce a substantially uniform nip pressure regardless of the cross-section of the nip 44. As best illustrated in FIGS. 3 and 5, each of thelink systems 82, 84 comprises a generally vertical first link or primary lever arm 86 which intermediate its ends carries a pivot pin 88 pivotally mounting the link 86 on a fixed support 90. The lower end of each first link 86 is pivotally connected by a pivot pin 92 to one end of a generally horizontal second or connecting link 94, the

opposite end of which is connected by a pivot pin 96 to the lower end of a generally vertical, bifurcated third link or secondary lever arm 98. As illustrated in FIGS. 5 and 7, the openings 118 in the links 94 receiving the pivot pins 96 are of vertical lengths substantially greater than the cross-sections of the pivot pins 96; and the pivot pins 96 are vertically centered in the openings 1 18 by springs and prevented from rotating by keys 122. Hence, the links 94 engage the pivot pins 96 in rolling contact to provide low friction connections between the links 94 and the pivot pins 96.

The upper ends of the third links 98 are pivotally mounted on fixed supports 100 by pivot pins 102 and each carry an integral link 104 which is generally S- shaped in vertical cross-section. The generally S- shaped links 104 are pivotally mounted in contact with pressure blocks 106 and pressure plates 108 which are received in the upper and lower recesses 110, 112 of the links 104 and mounted on the carriage blocks 64 and the platens 68, respectively; and hence the links 104 connect the link systems 82, 84 to the respective thereadjacent platens 68 and apply the pressing forces of the link systems 82, 84 to the roll 40. As shown in FIG. 6, leaf springs 114 are attached to the pressure blocks 106 by clamps 116, such leaf springs 114 serving to centralize the pressure blocks 106 in their recesses 110, 112.

The link systems 82, 84 are actuated by individual pressure fluid operated actuators, one of which is shown in FIG. 3 as 124. The actuators 124 each comprise a cylinder 126 containing a piston 128 provided with an extension rod 130 which is connected by a pivot pin 132 to the upper end of the first link 86 of the respective link system 82 or 84; and the pivot pin 132 and the beforedescribed pivot pins 88, 92 are each circumferentially provided with needle bearings or the like to minimize friction at their connections. Due to these needle bearings and the aforedescribed connections of the pivot pins 96 to the links 94, responsiveness of the linkage systems 82, 84 to changes in the feed rate of the suspension passing through the nip 44 is maximized. Each cylinder 126 is pivotally mounted on a fixed support 134; and the rod'ends of the cylinders 126 are connected by individual fluid lines 136 to a relatively large common source or tank 138 of constant pressure, pressurized fluid such as air. The tank 138 is connected to a conduit 140, in turn, communicating with an exhaust conduit 142 open to the atmosphere; and a valve designated generally as 144 is located intermediate the conduits 140, 142 for controlling the ex-' hausting of pressurized fluid through the conduits 140, 142. The valve 144 comprises a piston 146 biased by a spring 148 towards an open position in which the conduits 140, 142 communicate for exhausting pressurized air from the tank 138. The piston 146 is normally fluid biased to a closed position, preventing communication of the conduits 140, 142, by pressurized air supplied at constant pressure through a supply conduit 150 having interposed therein a control valve 152. The valve 152 is normally operated by a solenoid 154 to communicate the valve 144 through the conduit 150 with the source of the biasing fluid, but upon de-energization of the solenoid 154 is actuatable by a spring 156 to exhaust the biasing fluid from the valve 144 through an exhaust conduit 158 whereby the spring 148 is permitted to move the piston 146 to its aforedescribed open position. A switch designated generally as 160, mounted adjacent one of the third links 98 to be tripped by the latter after a predetermined degree of movement, is electrically connected to the solenoid 154 by an electrical lead 162 to de-energize the solenoid 154 upon its tripping. The head end of each cylinder 126 is provided with an exhaust conduit 164 for rapidly exhausting fluid therefrom.

The link systems 82, 84 are interconnected by control means controlling the link systems 82, 84 to cause the latter to maintain the axis of the press roll 40 parallel to the axis of the press roll 42. As best illustrated in FIG. 5, this control means comprises a connecting bridge in the form of a torsion bar 166 rigidly connected at its opposite ends to the first links 86 of the link systems 82, 84 co-axially with the pins 88. The torsion bar 166 hence, as will be seen, is responsive to movement of the link 86 of one of the link'systems 82, 84 to provide similar movement of the link 86 of the other thereof and in this manner insures the maintenance of the parallel axes of the rolls 40, 42.

During the normal operation of the press, the expansible tubes 70 are filled with pressurized air from the source 74 and exert constant equal biasing forces through the carriage blocks 62 on the ends of the press roll 40 to hold the latter spaced away from the press roll 42 by the nip 44. The rod ends of the cylinders 126 of the actuators 124 are supplied pressurized air from the tank 138, the piston 146 of the valve 144 being closed due to the energization of the solenoid 154; and the pistons 128 of the actuators 124 cause the link systems 82, 84 to exert pressing force on the ends of the pressing roll 40 through the platens 68, tie rods 66 and carriage blocks 62. Hence, the nip 44 is resultantly pressurized; and, due to the aforedescribed construction and arrangement of the links of the link systems 82, 84 and the constant pressure of the air in the cylinders 126 of the actuators 124, a constant uniform pressing force is maintained regardless of the width of the nip 44. The press rolls 40, 42 are continuously rotatably driven through the drive shaft 76 and the' gearing contained within the gear casings 78, 80; and the liquid suspension to be pressed is continuously supplied to the lower end of the vat through the inlet duct 18 and the inlet pipes 20 and inlet openings 22. The pressure of the supplied suspension causes a portion of its liquid content to flow through the porous circumferential walls 54 of the rolls 40, 42 to the channels 50 therein; and, as the suspension passes through the nip 44 between the rolls 4t), 42, the remaining portion of the liquid content of the suspension is pressed from the latter and also flows through the circumferential walls 54 to the channels 50. The pressed solid material is removed from the rolls 40, 42 by the doctor blades 46, 48 and is discharged through the discharge conduit 24 by the rotatably driven feed screw 26, the liquid in the discharge channels 50 being drained therefrom through the filtrate drainage conduits 58.

Throughout the normal operation of the press, the axis of the roll 40 is maintained parallel to that of the roll 42 and the pressing force applied to the roll 40 (and hence to the nip 44) by the link systems 82, 84 maintains the nip 44 pressurized with a substantially constant force regardless of the cross-section of the nip. In the event of the passage of foreign or tramp material longitudinally off-center through the nip 44, the movement of the end of the roll 44 most adjacent to the tramp material away from the roll 42 automatically and substantially simultaneously causes commensurate movement of the links of the link system 82 or 84 at that end of the roll 40 which, in turn, substantially immediately actuates the torsion bar 166 to provide identical movement of the other of the link systems 82 or 84. The low friction connections of the links 86, 94, 98 and the rod ends 130, substantially minimize the effects of friction on the link movement; and the pressurized air in the rod ends of the cylinders 126 of the actuators 124 displaced by the resultant movement of the pistons 128, of course, flows through the fluid lines 136 to the tank 138. Thus, the axes of the rolls 40, 42 are resultantly maintained parallel substantially throughout the normal press operation. Due to this maintenance of the rolls 40, 42 on parallel axes, the pressed material is maintained of uniform cross-section throughout the length of the nip 44, damage to the seals at the ends of the rolls 40, 42 is prevented, and the teeth of the gears drivingly interconnecting the rolls 40, 42 are maintained parallel to prevent their possible damage.

In the event that the roll 40 is moved away from the roll 42 such as might occur due to the passage of excessive or fluctuating suspension feed pressure or extremely large tramp material in the nip 44, the switch is tripped by the thereadjacent third link 98 de-energize the solenoid 154. Hence, the valve 152 is shifted by the spring 156 to exhaust pressurized air through the exhaust conduit 158, thus permitting the spring 148 to shift the piston 146 of the valve 144 to its open position whereby the tank 138 communicates with the exhaust conduit 142 and pressurized air is exhausted from the head ends of the cylinders 126 of the actuators 124. Thus, the pressure normally applied by the link systems 82, 84 is relieved to permit movement of the roll 40 away from the roll 42; and possible substantial damage is prevented. Also, as will be seen, the switch 160 could, if desired, be suitably electrically connected to cause further flow of suspension to the'nip 44 to be prevented and/or otherwise shutdown the press such as by stopping the driven rotation of the rolls 4t), 42.

From the preceding description it will be seen that the invention provides new and improved means for accomplishing all of the aforestated objects and advantages. lt will be understood however, that although only a single embodiment of the invention has been illustrated and hereinbefore described, the invention is not limited merely to this single embodiment, but rather contemplates other embodiments and variations with the scope of the following claims.

Having thus described our invention, we claim:

1. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-andaway from the other thereof to vary the cross-section of said nip, first means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, control means for causing said first and second force applying means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said first and second force applying means being spaced apart longitudinally of said movable press roll, said control means comprising connecting bridge means extending longitudinally along said movable press roll and interconnecting said force applying means to cause movement of one thereof to provide corresponding movement of the other thereof, and actuating means for actuating said first and second force applying means to apply said pressing force.

2. A press according to claim 1, wherein said actuating means comprises individual pressure fluid operated actuators for said force applying means, and said connecting bridge means is rigidly connected at opposite ends to said force applying means.

3. in a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-andaway from the other thereof to vary the cross-section of said nip, first link means actuatable for applying pressing force to said movable press roll and permitting tuating said first and second link means to apply said pressing force, and control means for causing said first and second link means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said control means comprising a torsion bar interconnecting said first and second link means responsive upon movement of one thereof to cause similar movement of the other thereof.

4. A press according to claim 3, wherein said link means comprises links interconnected by low friction connections,

5. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-andaway from the other thereof to vary the cross-section of said nip, first link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, said link means each comprising links interconnected by low friction connections, actuating means for actuating said first and force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, actuating means for actuating said first and second force applying means to apply said pressing force, and control means for causing said first and second force applying means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said first and second force applying means each comprising a plurality of interconnected links, said control means comprising a torsion bar connecting the links of each of said force applying means with the links of the other thereof whereby movement of the links of one of said force applying means causes similar movement of the links of the other thereof, and said actuating means comprising individual pressure fluid operated actuators for said force applying means and means for supplying pressurized fluid to said actuators to cause said links to yieldably bias said movable press roll towards said other press roll.

7. A press according to claim 3, wherein said actuat ing means comprises individual pressure fluid operated actuators for said link means.

8, A press according to claim 7, further comprising means responsive upon movement of said movable press roll away from said other press roll for causing pressurized fluid to be exhausted from said actuators.

9. A press according to claim 3, further comprising means intermediate said press rolls biasing said movable press roll from said other press roll.

10. A press according to claim 3, further comprising support means adjacent opposite ends of said movable press roll rotatably supporting said movable press roll, a plurality of tie rods connected to said support means and projecting on the opposite side of said other press roll from said movable press roll, and platen means on such opposite side of said other press roll connected to said tie rods for conjoined movement with said movable press roll, said first and second link means being connected to said platen means to apply pressing force to said movable press roll through said platen means and said tie rods.

11. A press according to claim 10, wherein said actuating means comprises individual fluid pressure operated actuators for said link means, and each of said link means comprises a first link connected to a respective one of said actuators, a second link connected to said first link, a third link connected to said second link, and connecting link means connected to said third link applying pressing force to said platen means.

12. in a press, a vat, inlet means for supplying a suspension to be pressed to said vat, discharge means for separately discharging pressed material and liquid from said vat, a plurality of press rolls rotatably in said for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second link means including a plurality of interconnected links actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, said first and second link means being spaced apart longitudinally of said movable press roll, torsion bar means interconnecting said first and second link means responsive upon movement of the links of one thereof to cause similar movement of the links of the other thereof whereby the axis of said movable press roll is maintained parallel to the axis of said other press roll, and individual pressure fluid operated actuators for causing said first and second link means to apply pressing force to said movable press roll.

13. A press according to claim 12, wherein links of each of said link means are connected by low friction connections.

M. A press according to claim 13, further comprising a common source for supplying pressurized fluid to said actuators, and means responsive upon movement of said movable press roll from said other press roll for causing pressurized fluid to be exhausted from said source and said actuators.

15. A press according to claim 12, further comprising support means adjacent opposite ends of said press rolls rotatably supporting said press rolls for rotation about their said axes, a plurality of tie rods each at one end connected to said support means for said movable press roll and projecting on the opposite side of said other press roll from said movable press roll, and platen means on said opposite side of said other press roll connected to said tie rods for conjoined movement with said movable press roll, said link means being connected to said movable press roll through said platen means and said tie rods.

16. A press according to claim 15, further comprising switch means actuatable upon movement of said link means to cause pressurized fluid to be rapidly exhausted from said actuators. l7. A press according to claim 15, wherein each said link means comprises a pivotally mounted first link connected at one end to the respective one of said actuators, a second link pivotally connected to the other end of said first link, a third link pivotally connected to said second link, and a fourth link connected to said third link and applying force to said platen means.

18. A press according to claim 17, wherein said fourth links are of generally S-shaped cross-section.

19. A press according to claim 18, further comprising low friction connections connecting said generally S-shaped links to said platen means and to a fixed support.

20. A press according to claim 18, wherein links of said link means are interconnected by low friction connections, and said means biasing said movable press roll from said other press roll comprises a plurality of pressure fluid operated actuators and a common source for supplying pressurized fluid to said actuators. 

1. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of said nip, first means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, control means for causing said first and second force applying means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said first and second force applying means being spaced apart longitudinally of said movable press roll, said control means comprising connecting bridge means extending longitudinally along said movable press roll and interconnecting said force applying means to cause movement of one thereof to provide corresponding movement of the other thereof, and actuating means for actuating said first and second force applying means to apply said pressing force.
 2. A press according to claim 1, wherein said actuating means comprises individual pressure fluid operated actuators for said force applying means, and said connecting bridge means is rigidly connected at opposite ends to said force applying means.
 3. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of said nip, first link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, actuating means for actuating said first and second link means to apply said pressing force, and control means for causing said first and second link means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said control means comprising a torsion bar interconnecting said first and second link means responsive upon movement of one thereof to cause similar movement of the other thereof.
 4. A press according to claim 3, wherein said link means comprises links interconnected by low frIction connections.
 5. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of said nip, first link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second link means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, said link means each comprising links interconnected by low friction connections, actuating means for actuating said first and second link means to apply said pressing force, and control means for causing said first and second force link to maintain the axis of said movable press roll parallel to the axis of said other press roll.
 6. In a press, a plurality of press rolls rotatably mounted for rotation about spaced axes and circumferentially spaced by a nip between said press rolls, one of said press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of said nip, first means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second means actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, actuating means for actuating said first and second force applying means to apply said pressing force, and control means for causing said first and second force applying means to maintain the axis of said movable press roll parallel to the axis of said other press roll, said first and second force applying means each comprising a plurality of interconnected links, said control means comprising a torsion bar connecting the links of each of said force applying means with the links of the other thereof whereby movement of the links of one of said force applying means causes similar movement of the links of the other thereof, and said actuating means comprising individual pressure fluid operated actuators for said force applying means and means for supplying pressurized fluid to said actuators to cause said links to yieldably bias said movable press roll towards said other press roll.
 7. A press according to claim 3, wherein said actuating means comprises individual pressure fluid operated actuators for said link means.
 8. A press according to claim 7, further comprising means responsive upon movement of said movable press roll away from said other press roll for causing pressurized fluid to be exhausted from said actuators.
 9. A press according to claim 3, further comprising means intermediate said press rolls biasing said movable press roll from said other press roll.
 10. A press according to claim 3, further comprising support means adjacent opposite ends of said movable press roll rotatably supporting said movable press roll, a plurality of tie rods connected to said support means and projecting on the opposite side of said other press roll from said movable press roll, and platen means on such opposite side of said other press roll connected to said tie rods for conjoined movement with said movable press roll, said first and second link means being connected to said platen means to apply pressing force to said movable press roll through said platen means and said tie rods.
 11. A press according to claim 10, wherein said actuating means comprises individual fluid pressure operated actuators for said link means, and each of said link means comprises a first link connected to a respective one of said actuators, a second link connected to said first link, a third link connected to said second link, and connecting link means connected to said third link applying pressing foRce to said platen means.
 12. In a press, a vat, inlet means for supplying a suspension to be pressed to said vat, discharge means for separately discharging pressed material and liquid from said vat, a plurality of press rolls rotatably in said vat for rotation about spaced parallel axes, said press rolls being circumferentially spaced by a therebetween nip and one of said press rolls being laterally movable towards-and-away from the other thereof to vary the cross-section of said nip, drive means connected to said press rolls for rotatably driving said press rolls, means adjacent opposite sides of said nip biasing said movable press roll from said other press roll, first link means including a plurality of interconnected links actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, second link means including a plurality of interconnected links actuatable for applying pressing force to said movable press roll and permitting lateral movement of said movable press roll away from said other press roll, said first and second link means being spaced apart longitudinally of said movable press roll, torsion bar means interconnecting said first and second link means responsive upon movement of the links of one thereof to cause similar movement of the links of the other thereof whereby the axis of said movable press roll is maintained parallel to the axis of said other press roll, and individual pressure fluid operated actuators for causing said first and second link means to apply pressing force to said movable press roll.
 13. A press according to claim 12, wherein links of each of said link means are connected by low friction connections.
 14. A press according to claim 13, further comprising a common source for supplying pressurized fluid to said actuators, and means responsive upon movement of said movable press roll from said other press roll for causing pressurized fluid to be exhausted from said source and said actuators.
 15. A press according to claim 12, further comprising support means adjacent opposite ends of said press rolls rotatably supporting said press rolls for rotation about their said axes, a plurality of tie rods each at one end connected to said support means for said movable press roll and projecting on the opposite side of said other press roll from said movable press roll, and platen means on said opposite side of said other press roll connected to said tie rods for conjoined movement with said movable press roll, said link means being connected to said movable press roll through said platen means and said tie rods.
 16. A press according to claim 15, further comprising switch means actuatable upon movement of said link means to cause pressurized fluid to be rapidly exhausted from said actuators.
 17. A press according to claim 15, wherein each said link means comprises a pivotally mounted first link connected at one end to the respective one of said actuators, a second link pivotally connected to the other end of said first link, a third link pivotally connected to said second link, and a fourth link connected to said third link and applying force to said platen means.
 18. A press according to claim 17, wherein said fourth links are of generally ''''S''''-shaped cross-section.
 19. A press according to claim 18, further comprising low friction connections connecting said generally ''''S''''-shaped links to said platen means and to a fixed support.
 20. A press according to claim 18, wherein links of said link means are interconnected by low friction connections, and said means biasing said movable press roll from said other press roll comprises a plurality of pressure fluid operated actuators and a common source for supplying pressurized fluid to said actuators. 